Hyperkalemic periodic paralysis
| Hyperkalemic periodic paralysis | |
|---|---|
| Classification and external resources | |
| Specialty | neurology |
| ICD-10 | G72.3 |
| ICD-9-CM | 359.3 |
| OMIM | 170500 |
| DiseasesDB | 6252 |
| MedlinePlus | 000316 |
| eMedicine | article/1171678 |
| MeSH | D020513 |
| GeneReviews | |
Hyperkalemic periodic paralysis (HYPP, HyperKPP) is a genetic disorder. It occurs in humans, horses (where it is also known as Impressive syndrome, after an index case in a horse named Impressive, or possibly one of his ancestors), and perhaps other animals. It is an inherited autosomal dominant disorder that affects sodium channels in muscle cells and the ability to regulate potassium levels in the blood. It is most commonly associated with horses, but occurs in humans, where it may be called Gamstorp episodic adynamy. It is characterized by muscle hyperexcitability or weakness which, exacerbated by potassium, heat or cold, can lead to uncontrolled shaking followed by paralysis. Onset in humans usually occurs in early childhood, but still occurs with adults.
The mutation which causes this disorder is dominant on SCN4A with linkage to the sodium channel expressed in muscle. The mutation causes single amino acid changes in parts of the channel which are important for inactivation. In the presence of high potassium levels, including those induced by diet, sodium channels fail to inactivate properly.
Equine hyperkalemic periodic paralysis occurs in 1 in 50 Quarter Horses and can be traced to a single ancestor, a stallion named Impressive.
This inherited disease is characterized by violent muscle twitching and substantial muscle weakness or paralysis among affected horses. HYPP is a dominant genetic disorder; therefore, heterozygotes bred to genotypically normal horses have a statistic probability of producing clinically affected offspring 50% of the time.
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